Salts of diamines and tetrahalophthalates

ABSTRACT

(Cyclo)alkylenediammonium compounds corresponding to the formula: ##STR1## wherein X is halogen, R is an alkylene or cycloalkylene group containing 2-15 carbon atoms, each R&#39; alone is an alkyl, cycloalkyl, or aralkyl group, and R&#39;---R&#39; together represent an alkylene, cycloalkylene, or aralkylene group are prepared by esterifying a tetrahalophthalic anhydride with a mono- or dihydroxyalkane, -cycloalkane, or -aralkane having a boiling point below 250° C. to form a half-ester and then reacting the half-ester with a stoichiometric amount of a diaminoalkane or diaminocycloalkane containing 2-15 carbon atoms. 
     The (cyclo)alkylenediammonium compounds of the invention are useful as flame retardants for normally flammable organic polymers and also have utility as intermediates for the preparation of N,N&#39;-(cyclo)alkylene-bis-tetrahalophthalimides, which are also useful as flame retardants. The imides are prepared simply by heating the diammonium compounds.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to novel (cyclo)alkylenediammonium salts oftetrahalophthalate half-esters and to bisimides prepared therefrom.

2. Description of the Prior Art

As taught in U.S. Pat. No. 3,873,567 (Cyba), British patent 1,287,934(Raychem), and Sydney M. Spatz and Herman Stone, "Some N-SubstitutedTetrabromophthalimide Fire-Retardant Additives," INDUSTRIAL ANDENGINEERING CHEMISTRY PRODUCT RESEARCH AND DEVELOPMENT, Volume 8, pp.397-398 (1969), N,N'-alkylenebis-tetrahalophthalimides having utility asflame retardants can be prepared by reacting a tetrahalophthalicanhydride with a diaminoalkane in an organic solvent medium. Theseprocesses, which produce the bisimides via an amic acid intermediatecorresponding to the formula: ##STR2## are difficult to control, presentfiltration problems, and are less economical than is desirable.

SUMMARY OF THE INVENTION

An object of this invention is to provide a novel process for preparingN,N'-(cyclo)alkylene-bis-tetrahalophthalimides.

Another object is to provide such a process which is economical, easilycontrolled, and conducive to the formation of a readily filterableproduct.

A further object is to provide such a process which leads to theformation of the bisimides via novel intermediates.

A still further object is to provide novel intermediates which areuseful as flame retardants as well as having utility in the formation ofbisimides.

These and other objects are attained by (1) esterifying atetrahalophthalic anhydride with a mono- or dihydroxyalkane,-cycloalkane, or -aralkane having a boiling point below 250° C. to forma half-ester corresponding to the formula: ##STR3## wherein X is halogenand R' is an alkyl, cycloalkyl, or aralkyl group, or a half-estercorresponding to the formula: ##STR4## wherein X is halogen and R' is analkylene, cycloalkylene, or aralkylene group, (2) reacting the resultanthalf-ester with a stoichiometric amount of a diaminoalkane ordiaminocycloalkane containing 2-15 carbon atoms to form an alkylene- orcycloalkylenediammonium compound corresponding to the formula: ##STR5##and, when a bisimide is desired, (3) recovering the diammonium compoundand (4) heating it at about 125-250° C. until it reaches constantweight, indicating the formation of anN,N'-(cyclo)alkylene-bis-tetrahalophthalimide corresponding to theformula: ##STR6## wherein X is halogen and R is an alkylene orcycloalkylene group containing 2-15 carbon atoms.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The tetrahalophthalic anhydride that is esterified in the practice ofthe invention is usually tetrabromophthalic anhydride,tetrachlorophthalic anhydride, or a mixture thereof; and it ispreferably tetrabromophthalic anhydride.

As indicated above, the alcohol that is reacted with thetetrahalophthalic anhydride in the practice of the invention can be anymono- or dihydroxyalkane, -cycloalkane, or -aralkane having a boilingpoint below 250° C. However, for reasons of availability, it ispreferably an alcohol containing 1-12 carbon atoms, more preferably 1-6carbon atoms, and it is most preferably methanol or ethylene glycol.Exemplary of other alcohols that can be used are ethanol; propanol;isopropyl alcohol; the normal, secondary, tertiary, and isobutylalcohols; the pentanols; the hexanols; the decanols; cyclohexanol;benzyl alcohol; propylene glycol; butylene glycol; cyclohexandiol;xylylene glycol, etc., and mixtures thereof.

As indicated above, the diaminoalkane or diaminocycloalkane that is usedin the practice of the invention can be any such compound containing2-15 carbon atoms. However, it is preferably a diaminoalkane containing2-6 carbon atoms and most preferably 1,2-diaminoethane. Exemplary ofother diamines that can be used are 1,2-diaminopropane,1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane,1,6-diaminohexane, 1,2-diaminocyclohexane, 1,12-diaminododecane,4,4'-methylene-bis-cyclohexylamine, etc.

The manner of esterifying the anhydride with the alcohol is notcritical. Formation of the half-ester may be accomplished simply bycontacting the reactants in a suitable reaction medium at a suitablereaction temperature, usually a temperature in the range of about20-200° C., and, when necessary, applying superatmospheric pressure toprevent the boiling that would otherwise occur at the higher reactiontemperatures. However, it is preferred to conduct the reaction at refluxtemperature. Most conveniently the reaction medium is an excess of thealcohol, but it may be any inert solvent boiling above about 60° C.,e.g., at about 60-200° C. Exemplary of such solvents are benzene,xylene, toluene, chlorobenzene, chloroform, etc., and mixtures thereof.The total amount of reaction medium employed for the esterification,although not critical, is conveniently such as to provide a solidscontent of about 5-80%, preferably about 5-70%, and most preferablyabout 25-50%, by weight when the diamine is added for the subsequentstep of the synthesis.

The reaction of the diamine with the half-ester is most suitablyaccomplished by adding the diamine to the reaction mixture resultingfrom the esterification reaction at a temperature in the range of about50-200° C., superatmospheric pressures being employable when they aredesired to prevent boiling. It is advantageous to conduct the reactionat reflux temperature. It is also advantageous to conduct the reactionby adding the diamine gradually to the reaction mixture, e.g., over aperiod of about 0.25-4 hours, and then continuing to heat the reactionmixture for at least about 45 minutes, frequently for about 0.75-2hours. The product may then be recovered by conventional cooling,filtering, and drying techniques.

When the diammonium compound thus obtained is desired only as anintermediate for the preparation of a bisimide, it may then be convertedto the bisimide by heating it at about 125-250° C. until it reachesconstant weight. The time required for this reaction varies with theparticular temperature employed but is usually in the range of about1-48 hours, the shorter times being sufficient at the highertemperatures and the longer times sometimes being required at the lowertemperatures.

The invention is advantageous in that it provides an economical andeasily controlled process for preparingN,N'-(cyclo)alkylene-bis-tetrahalophthalimides, which have known utilityas flame retardants, and it is conducive to the formation of a readilyfilterable product. It is also advantageous in that the process leads tothe formation of the bisimides via novel diammonium intermediates whichare useful per se as flame retardants.

The following examples are given to illustrate the invention and are notintended as a limitation thereof.

EXAMPLE I Part A

Charge 240 g. of methanol and 150 g. of tetrabromophthalic anhydride toa suitable reaction vessel. Heat the reaction mixture at reflux for twohours, and add a solution of 9.69 g. of 1,2-diaminoethane in 10 g. ofmethanol over a period of 30 minutes. Continue refluxing for anadditional 90 minutes. Then cool to 25° C., filter, and air dry theproduct. The process results in the formation of 149 g. ofethylenediammonium-bis-methyl tetrabromophthalate, a white crystallinematerial. Infra-red and thermogravimetric analyses support theidentification of the product.

Part B

Heat the product of Part A in a vacuum oven at 136° C. for 16 hours. Theprocess results in 99.8% conversion toN,N'-ethylene-bis-tetrabromophthalimide.

EXAMPLE II

Repeat Example I except for replacing the fresh methanol with recoveredmother liquor from Example I. The ethylenediammonium-bis-methyltetrabromophthalate is obtained in 95% yield.

EXAMPLE III

Repeat Example I except for replacing the methanol with ethylene glycol.The product of Part A is ethylenediammoniumethylene-bis-tetrabromophthalate. The product of Part B isN,N'-ethylene-bis-tetrabromophthalimide.

EXAMPLE IV

Repeat Example I except for replacing the 1,2-diaminoethane with anequimolar amount of 1,2-diaminopropane. The product of Part A is(1,2-propylene)diammonium-bis-methyl tetrabromophthalate. The product ofPart B is N,N'-(1,2-propylene)-bis-tetrabromophthalimide.

EXAMPLE V

Repeat Example I except for replacing the 1,2-diaminoethane with anequimolar amount of 1,3-diaminopropane. The product of Part A is(1,3-propylene)diammonium-bis-methyl tetrabromophthalate. The product ofPart B is N,N'-(1,3-propylene)-bis-tetrabromophthalimide.

EXAMPLE VI

Repeat Example I except for replacing the 1,2-diaminoethane with anequimolar amount of 1,6-diaminohexane. The product of Part A ishexamethylenediammonium-bis-methyl tetrabromophthalate. The product ofPart B is N,N'-hexamethylene-bis-tetrabromophthalimide.

Similar results are observed when the examples are repeated except thatone or more ingredients are replaced by materials taught to be theirequivalents in the specification.

It is obvious that many variations can be made in the products andprocesses set forth above without departing from the spirit and scope ofthis invention.

What is claimed is:
 1. A bis-tetrahalophthalate corresponding to theformula: ##STR7## wherein X is halogen, R is an alkylene orcycloalkylene group containing 2-15 carbon atoms, each R' alone is analkyl, cycloalkyl, or aralkyl residue of a monohydric alcohol having aboiling point below 250° C., and R'--R' together represent an alkylene,cycloalkylene, or aralkylene residue of a dihydric alcohol having aboiling point below 250° C.
 2. The bis-tetrahalophthalate of claim 1wherein X is bromine.
 3. The bis-tetrahalophthalate of claim 1 wherein Xis chlorine.
 4. The bis-tetrahalophthalate of claim 1 wherein R is analkylene group containing 2-6 carbon atoms.
 5. Thebis-tetrahalophthalate of claim 4 wherein R is a 1,2-ethylene group. 6.The bis-tetrahalophthalate of claim 1 wherein each R' is an alkyl,cycloalkyl, or aralkyl group containing 1-12 carbon atoms.
 7. Thebis-tetrahalophthalate of claim 6 wherein each R' is an alkyl groupcontaining 1-6 carbon atoms.
 8. The bis-tetrahalophthalate of claim 7wherein each R' is methyl.
 9. The bis-tetrahalophthalate of claim 1wherein X is bromine, R is a 1,2-ethylene group, and each R' is methyl.10. The bis-tetrahalophthalate of claim 1 wherein R'--R' togetherrepresent an alkylene, cycloalkylene, or aralkylene group containing2-12 carbon atoms.
 11. The bis-tetrahalophthalate of claim 10 whereinR'--R' together represent an alkylene group containing 2-6 carbon atoms.12. The bis-tetrahalophthalate of claim 11 wherein R'--R' togetherrepresent an ethylene group.